1. Field
The present invention relates to a pneumatic tire tread, and in further detail, to a pneumatic tire tread with which flexible fences are formed in the primary groove of the tread and it is thereby possible to reduce air column resonance and maintain water drainage performance while ensuring that the flexible fences and tread portion will be abraded to a similar extent.
2. Description of Related Art
The air column resonance of a primary groove formed in the tread of a tire is generated by resonance inside a tube (air column) formed between the primary groove and the road surface, and this resonance frequency depends on the length of the air column of the primary groove formed with the road surface.
This air column resonance is manifested in the form of noise inside and outside the vehicle and often peaks at approximately 1 kHz, which is audible to the human ear. Technology for reducing the air column resonance of the primary groove includes disposing so-called flexible fences, that is, projections, which extend from the groove walls or groove base of the primary groove and block all or the majority of the primary groove such that the air column resonance is reduced by blocking the flow of air in the direction in which the primary groove is formed. Nevertheless, when the tire runs on a wet road surface, the water that has entered the primary groove is prevented from flowing through the primary groove because air is prevented from flowing in the direction in which the primary groove is formed. There is therefore a reduction in drainage of water between the pneumatic tire and the road surface and as a result, there is a reduction in operating safety on wet road surfaces.
FIG. 4 of patent document 1 discloses technology that serves to reduce air column resonance and impart water drainage wherein three group fences 3 (flexible fences) that extend from opposing walls on the inside of the groove and the groove base, respectively, are disposed such that they are each separated by a space.
Moreover, FIG. 3 of patent document 2 discloses technology that serves to reduce air column resonance and improve water drainage by disposing a diaphragm 30 (flexible fence) that extends from the groove base inside the primary groove such that the majority area from the opening in the primary groove does not contact the groove walls.    [Patent document 1] JP-A H11-105511    [Patent document 2] JP-A 2006-341655